This invention relates to hoisting apparatus, and in particular to a height-adjustable hoist adapted to be mounted within, and operated from, the bed of a truck.
One important object of the present invention is to provide a portable hoist having a hoist arm which is pivotable to place the free end of the arm at different adjusted heights and, a simple mechanism for maintaining the free end of the hoist arm at a desired height.
It is another object of the invention to provide a height-adjustable hoist capable of supporting heavy loads.
Yet another object of the invention is to provide an extendible hoist designed to be stationarily mounted within the bed of a truck, with collapsible mast structure in the hoist collapsed to a height which may be substantially that of the sides of the truck.
In a particular embodiment of the present invention, the height-adjustable hoist comprises an upright tubular post adapted to be stationarily mounted on the floor of a truck bed, or the like. Rotatably mounted on the top of the post is a sleeve. A cylindrical tip member is rotatably mounted within the post, and is also slidably extensible from the post, thereby to be slideably positionable between a lowered position in which the top of the tip member is adjacent the upper portion of the post, and a raised position wherein the same are spaced apart. The tip member and post constitute extendible and contractible mast structure in the hoist. A hoist arm is mounted at one of its ends to the sleeve for pivoting in a substantially upright plane. Provided on the hoist arm is a hoist line, a pulley about which the line is trained, and a drum for taking in and paying out the line.
A nonextensible chain extending from the other end of the hoist arm to the top of the tip member serves to establish the angle of the hoist arm in relation to the post. A chain lock on the tip member permits the effective length of the chain to be selectively varied. In operation, the hoist arm is suitably oriented and raised to place it at the desired operating position. The tip member is then raised and the chain is selectively locked in a position wherein the chain is stretched between the tip member and the hoist arm. With the chain in place, the tip member is maintained in its extended position and the angular position of the hoist arm is maintained.
Other objects and features of the present invention will become more apparent from the following detailed description of a preferred embodiment of the invention, and the accompanying drawings.